Furnace underhearth cooling apparatus



April 16, 1968 G. L .FRENCH ETAL FuRNAcE UNDERHEARTH coomne APPARATUS 2Sheets-Sheet 1 April 16, 1968 G. L.. FRENCH ET AL 3,378,249

FURNACE UNDERHEARTH COOLING APPARATUS 2 Sheets-Sheet 2 Filed Dec. 8,1964 INVENTORS Ge orge L. Franc/1 h/i//iam G. Seacresf United StatesPatent O 3,378,249 FURNACE UNDERHEARTH COOLING APPARATUS George L.French, Center Valley, and William G.

Seacrest, Limeport, Pa., assignors, by mesne assignments, to BethlehemSteel Corporation, a corporation of Delaware Filed' Dec. 8, 1964, Ser.No. 416,784 Claims. (Cl. 266-32) ABSTRACT OF THE DISCLOSURE A compositecooler interposed between the hearth of a blast furnace and itsfoundation to cool the hearth bottom. The composite cooler is formed ofseveral spaced sections each having cooling fluid inlet and outletducts. The sections are connected at their peripheries so that outwardexpansion is restrained while inward expansion toward the hottest innerarea beneath the hearth is permitted.

This invention relates to means for cooling hearth bottoms ofmetallurgical shaft furnaces and more particularly to improved means forunderhearth cooling of carbon lined hearths of iron-making blastfurnaces.

The temperature of molten iron in the hearth of a blast furnace exceeds2600 F. Because of this high temperaature it has `been necessary toprovide some form of cooling for these hearths. During the years whenblast furnace hearths were lined exclusively with fire clay refractoriesthe conventional manner of cooling the hearth was by means of a waterjacket around the circumference of the cylindrical side wall.

As is well known, carbon is now being utilized in place of lire clay inhearth linings, because carbon can withstand higher temperatures, has alower thermal expansion, is a `better conductor of heat, is lighter inweight and is more resistant to chemical attack and corrosion. Becauseof these superior properties carbon hearth linings last longer than -reclay linings, produce more iron tonnage between relinings, and are lesssusceptible to iron penetration and breakout. Hearths made of carbon,because of the higher rate of heat conductivity of this material, morereadily transmit heat to hearth coolers thereby causing the iron freezeline, approximately 2100 F., to remain closer to the inner surface ofthe hearth than was previously the case with re clay lin-ings.

Cooling the bottom of a blast furnace hearth, lined with either carbonor lire clay, poses a number of serious problems. Many large blastfurnaces have hearth diameters which exceed twenty-six feet, and fromthe center to the outer periphery of the bottom of the linings of thesehearths the temperature gradient may exceed 1600 F. Any cooling systeminstalled beneath a blast furnace hearth must be designed to withstandthis large temperature differential and, above all, must remain sealedso that there is no leakage of the cooling medium into the hearthbottom. Leakage of water or air, the cooling mediums most frequentlyused, into a hearth bottom will create a serious situation. Molten metalin Contact with water will react with explosive violence, and in thecase of a carbon lined hearth any leakage of air into the hearth willcause the carbon to burn rapidly.

Therefore it is a object of the present invention to provide an improvedcooling means for carbon lined blast furnace hearths.

It is a `further object of this invention to provide an improved carbonlined hearth cooling means which will remain sealed whilecompensatingfor the differential temperature expansion and contraction caused by thetemper- ICC ature gradient between the center and outer periphery of thehearth and `due to variations in furnace operating ternperatures. y

It is a still further object of this invention to provide an improvedcooling means which will effectively cool the entire 'bottom area of ablast lfurnace hearth.

The objects and advantages of this invention will be more clearlyunderstood from the following description with reference to theaccompanying drawings in which:

FIGURE 1 is a vertical sectional view of a portion of the bottom of ablast furnace which has a carbon lined hearth and which is equipped withthe cooling means of this invention.

FIGURE 2 is a plan view of the improved blast furnace underhearthcooling means of this invention with the top removed from one section toshow, in detail, its internal construction. The outline of the furnaceshell is indicated diagrammatically by a broken line, and a smallportion of the shell plate is shown in cross section on the lower lefthand portion of the cooling means.

FIGURE 3 is a sectional View on an enlarged scale taken on line 3-3 ofFIGURE 2.

FIGURE 4 is a section-al view on an enlarged scale taken on line 4--4 ofFIGURE 2.

Referring in detail to the drawings there is shown blast furnace hearth1l) which comprises steel jacket 11, surrounded by heat exchange jacket12- which provides a means of cooling the periphery of the hearth,circular side Wall 13, and bottom 14. Hearth side wall 13 and bottom 14may be formed of any satisfactory material but, preferably, standardcarbon bricks 15 are used in side wall 13 and large carbon blocks 16 areused for hearth bottom 14. Directly beneath hearth bottom t4 iscomposite cooler 17, hereinafter more fully described, which is securelywelded to hearth jacket 11 at its lower end. Foundation 18 supports thefurnace structure. Leveling grout 19, as in conventional construction,is forced, under pressure, between cooler 17 and foundation 18.

Although our invention can be embodied in different forms, we prefer touse a composite cooler constructed in a manner as shown in FIGURES 1-4.Cooler 17 cornprises a plurality of cooler sections 2t)V which areseparated from one another by spaces 21, except at the outer ends of thecooler where sections 2t) are joined together by means of top closureplates 22, outer closure plates 12, and inner closure plates 24, asshown in detail inV FIGURE 4, in a manner hereinafter described.

Each cooler section 20 includes relatively thick upper plate 25, adaptedto be disposed directly next to carbon hearth bottom 14, lower plate 26,inner end plate 27, side plate or plates 28, extending longitudinally ofeach section, and outer end or peripheral plate 29. These elements arejoined together with continuous welds so that each cooler section 20 issealed to prevent any leakage of the cooling medium. Within each coolersection 20 a plurality of spaced apart separators 30, as for exampleT-bars, extend vertically between upper plate 25 and lower plate 26 andhorizontally, longitudinally of each section and parallel to side plateor plates 28, between inner end plate 27 and outer end or peripheralplate 29. These separators 30 divide each cooler section 20 into aplurality of `cooling chambers 3l. In each chamber 31 a baille 32, alsomade of Tebars, extends` vertically between upper plate 25 and lowerplate 26 and horizontally, parallel to separators 30, from outerperipheral plate 29 to a short distance from inner end plate 2.7 therebydividing each chamber 31 into inlet passageway 33 and outlet or exhaustpassageway 34. Near the outer end of each chamber inlet passageway 33 isinlet opening 35 in lower plate 26, and near the outer end of eachchamber outlet or exhaust passageway 34 is exhaust opening 36 in upperplate 25.

As shown in FIGURE l, a separate inlet manifold 37 is welded to theunderside of lower plate 26, at its outer periphery, of each coolersection 20. Each inlet manifold 37 extends beneath all the inletopenings 35 of its separate cooler section. Naturally, the separatecooler sections 2d and inlet manifolds 37 can be fabricated in anymanner desired, but preferably outer end plate 29 of each cooler sectionis extended downwardly to also form the outer wall plate 29' of themanifold, and manifolds 37 and cooler sections 26 are fabricated as oneunit, An inlet duct 3S connects each inlet manifold 37 to a coolingfluid source, not shown. An exhaust offtake 39 registers with each upperplate exhaust opening 36 and connects each cooler section chamberexhaust passageway 34 with exhaust manifold 40, which may serve one ormore cooler sections. Each manifold di) exhausts to the atmospherethrough duct 41. Within each exhaust offtake 39 is valve 42 whichregulates the cooling medium flow from each separate chamber 31 of eachcooler section 26. Preferably, the diameter of bottom cooler 17 is madesorncwhat larger than the diameter of hearth jacket 11 so that the inletand exhaust ductwork can be easily connected to cooler sections 20.

As mentioned above, the separate sections 26 of composite cooler 17 areseparated by spaces 21 except at the outer ends of the sections wherethey are joined together by closure plates 22, 23 and 24, as shown indetail in FIGURE 4. Top closure plates 22 extend between adjacent coolersection upper plates 25 from their outer periperal ends inwardly to aposition just within shell jacket 11, directly beneath hearth bottom 14.Outer closure plates 23 extend between outer peripheral plates 29 ofadjacent cooler sections 2) and between outer wall plates 29', for thefull height of these plates, of adjacent manifolds 37. Inner closureplates 2li extend between adjacent cooler sections 26 downwardly fromthe inner end of top closure plates 22 to an elevation below that oflower plates 26. Spaces 21 between adjacent cooler sections 29, exceptbetween inner closure plates 24 and outer closure plates 23 are filledwith a compressible device or material 43, as for example a lime bondedvermiculite, such as Thermoake. Spaces 21 between inner closure plates24 and outer closure plates 23 joining adjacent cooler sections 20 arelled with grout 19 at the same time that this material is forced betweenthe cooler 17 and foundation 18.

In the operation of the improved composite coo-ler 17 of this invention,the cooling medium, preferably air, travels through separate ducts 38 toeach section 2t? of the cooler. At each cooler section 20 air passesfrom its inlet manifold 37 through inlet openings 35 at the outerperiphery of lower plate 26 into a plurality of cooling chambers 31.Within each cooling chamber 31 air enters inlet passageway 33, flows tothe inner end of the chamber then reverses its flow, following a patharound bafiie 32, and passes through outlet passageway 34 and from thecham-ber through outlet opening 36. Exhaust offtakes 39, manifolds 40,and ducts 41 carry the heated air to the atmosphere. Cfttake valves 42in each exhaust offtake 39 are used to balance the ow of air through theplurality of chambers 31 of the several Sections 20 of composite cooler18. ln the event a cooling medium other than air is used, the coolingmedium can, instead of being exhausted to the atmosphere, be cooled andrecirculated through the system.

The major advantage of employing the composite cooler constructiondisclosed above is that the individual cooler sections, which each actas a separate cooler, can expand freely beneath the hearth, toward itsinner hottest area. The outer ends of the sections are joined so thattheir outward expansion is restrained, to a great degree, and thisrestraining influence forces the expansion to take place toward thehearth center. Sealing of the spaces between the outer ends of thecooler sections by means of closure plates and grout prevents anyinfiltration of air 4 through these spaces into the hearth bottom. Theincorporation of the compressible material in the remainder of each ofthese spaces prevents air from occupying them initially duringconstruction and later allows the cooler sections to expand into atleast a portion of the space previously occupied by this refractorymaterial as it is compressed. On added adavntage of employing aplurality of cooler sections with a plurality of cooling chambers isthat the hearth can be uniformly cooled and any hot spots can be easilyand accurately located and remedial action taken.

While the composite cooler heretofore described is particularly adaptedfor nnderhearth cooling of iron making blast furnaces, it will beunderstood that such a cooler can be used to advantage in many othertypes of furnaces where a uniform and efficient cooling is required.

While we have shown and described only one embodiment of our invention,it will be understood that this embodiment Iwas merely for the purposeof illustration and description and that there may be variousembodiments within the general scope of the invention and the scope ofthe appended claims.

We claim:

1. A composite cooler for cooling the underside of a furnace hearthcomprising:

(a) a plurality of separate cooler sections,

(b) a space between each pair of said cooler sections,

(c) means to allow a cooling medium to pass into each of said coolersections,

(d) means to allow a cooling medium to pass out of each of said coolersections,

(e) means at the outer periphery of said hearth joining said sectionstogether to restrain outward eX- pansion of said cooler sections and topermit inward expansion thereof due to a temperature differentialbetween the outer periphery and the inner area of the underside of saidhearth,

(f) sealing means extending between each pair of said cooler sections atthe outer periphery thereof to prevent infiltration of air into saidspace between each pair of said cooler sections and into the bottom ofsaid furnace hearth.

2. A composite cooler for cooling the underside of a furnace hearthcomprising:

(a) a plurality of separate cooler sections,

(b) a space between each pair of said cooler sections,

(c) means to allow a cooling medium to pass into each of said coolersections,

(d) means to allow a cooling medium to pass out of each of said coolersections,

(e) means at the outer periphery of said cooler sections joining saidsections together whereby outward expansion of said cooler sections dueto temperature differential between the outer periphery and the innerarea of the underside of said hearth is restrained and inward expansionis permitted,

(f) compressible means in said space between each pair of said coolersections to compensate for expansion of said sections at elevatedtemperatures.

3. A composite cooler for cooling the underside of a furnace hearthcomprising:

(a) a plurality of separate cooler sections, each said sectioncomprising:

( l) dividing means separating each said color section into a pluralityof cooling chambers, (2) means to allow a cooling medium to pass intoeach of said cooling chambers, and (3) means to allow a cooling mediumto pass out of each of said cooling chambers,

(b) a space between each pair of said cooler sections,

and

(c) means at the outer periphery of said hearth joining said sectionstogether to restrain outward expansion of said cooler sections and topermit inward expansion thereof due to a temperature differentialbetween 5 the outer periphery and the inner area of the underside ofsaid hearth,

(d) sealing means extending between each pair of said cooler sections atthe outer periphery thereof to prevent infiltration of air into saidspace between each pair of said cooler sections and into the bottom ofsaid Vfurnace hearth.

4. A composite cooler for cooling the underside of a furnace hearthcomprising:

(a) a plurality of separate cooler sections, each said sectioncomprising:

( 1) dividing means separating each said cooler section into a pluralityof cooling chambers, (2) means to allow a cooling medium to pass intoeach of said cooling chambers, and (3) means to allow a cooling rnediumto pass out `of each of said cooling chambers,

(b) a space between each pair of said cooler sections,

(c) means at the outer periphery of said cooler sections joining saidsections together whereby outward expansion of said cooler sections dueto a temperature differential between the outer periphery and the innerarea of the underside of said hearth is restrained and inward expansionis permitted,

(d) compressible means in said space between each pair of said coolersections to compensate for expansion of said sections at elevatedtemperatures.

5. A composite cooler, through which passes a cooling medium, forsupporting and cooling the underside of a furnace hearth comprising:

(a) a plurality of separate cooler sections, each said sectioncomprising:

( 1) a top horizontal plate, (2) a bottom horizontal plate, (3) avertical outer peripheral plate, (4) vertical enclosing plates, (5)dividing means, extending inwardly from said outer peripheral plate andvertically between said top plate and said bottom plate, sepa ratingeach said cooler section into agpluralit of cooling chambers, (6) meansto allow said cooling medium to pas into each of said cooling chambers,and (7) means to allow said cooling medium to pas out of each of saidcooling chambers, (b) a space between each pair of said cooler sections(e) closure means in each said space, at the outer end thereof extendinginwardly therefrom to a locatio: directly beneath said hearth, torestrain outward ex pansion of said cooler sections due to a temperaturdifferential between the outer periphery and th' vinner area of theunderside of said hearth and tt permit inward expansion thereof, and (d)compressible rneansin said space to compensatl for expansion of saidsections at elevated tempera tures.

References Cited UNITED STATES PATENTS 2,238,038 4/ 1941 Clutts 266--32,2,407,047 9/ 1946 West 266--31 )1 2,671,658 3/1954 Moore 266-322,697,598 12/ 1954 Atileck 266-31 2,991,061 7/ 1961 Boron 263--44 i3,053,524 9/ 1962 Hoadley et a1 266--32 FOREIGN PATENTS 707,697 4/ 1954Great Britain.

OTHER REFERENCES Under-Hearth `Cooling for Blast-Furnaces, Summers E.M.,Journal of the Iron and Steel Institute, August 1960 pp. 405-409.

J. SPENCER OVERHOLSER, Primary Examiner. E. MAR, Assistant Examiner.

